A lead frame is a metal substrate supporting a semiconductor chip. The lead frame is widely used for packaging a semiconductor device in an electronic component field. Recently, a semiconductor package, wherein a semiconductor device (for example, a lighting emitting diode (LED) chip) is mounted in the lead frame and a sealing material is injected, is used in various fields. The lead frame may be applied in various applications according to a form and a size thereof.
A light emitting diode (LED) among the semiconductors has been recently widely used because of its long life and eco-friendly characteristic. Particularly, in a lighting field, a usage of the LED is gradually increased by reason of a price fall of the LED, an incandescent light bulb ban and a fluorescent light bulb ban in each country, and the like.
However, the LED itself generates the large amount of heat, so that an LED package may cause a problem such as a defective product, degradation of a product quality and a decrease in product life, due to degradation of a thermal property.
Accordingly, in designing the semiconductor package, particularly, the LED package, a heat radiation design is very important. The important point is how to design the heat radiation structure so that heat is dischargeable to the outside by effectively transmitting thermal energy caused by a temperature difference.
In general, the heat radiation of a product has been accomplished by based on the view that considers the semiconductor device and the lead frame as one package, designing a printed circuit board (PCB) made of a metal or ceramic having high thermal conductivity, and then attaching a heat sink or a heat radiating means made of a metal onto a rear portion of the PCB. Heat generated in the package may be discharged to air through the PCB and the heat radiating means.
As described above, the prior art lead frame package is a structure accommodating the semiconductor chip in accordance with its size and shape and cannot be used itself. It may be used only through a heat radiation design such as an additional circuit design and a heat sink. That is, most of the LED packages discharge heat of the LED device to air through a separate heat radiating means such as a heat sink.
However, most of the LED products including a separate heat radiating means such as heat sink, have a large volume and limitations in a form, a shape, and a usage of a product due to a volume and a shape of the separate heat radiating means itself. Accordingly, the LED product so far has problems in that the product has a large volume, the product is heavy, a manufacturing time of the product is long, and the like.
In order to solve the problem, Korean Patent No. 1,340,029 discloses a technology of a lead frame for a semiconductor package, which is capable of providing excellent semiconductor chip performance even without using a separate heat radiating means. The patent is different from the prior art semiconductor package in that a lead frame itself is used as a heat radiating means. However, in the patent, a heat radiating characteristic of the lead frame is not still satisfied. Accordingly, a semiconductor package having a more excellent heat radiating characteristic has been demanded.